CN212909356U

CN212909356U - Soft start auxiliary power supply circuit

Info

Publication number: CN212909356U
Application number: CN202021779162.7U
Authority: CN
Inventors: 张鑫成; 邵攀峰; 张明村
Original assignee: East Group Co Ltd
Current assignee: East Group Co Ltd
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2021-04-06
Anticipated expiration: 2030-08-24

Abstract

The utility model discloses a soft start auxiliary power supply circuit, include: the rectification circuit is used for rectifying alternating current output by the alternating current power supply; the first filter capacitor is used for filtering the rectified direct current; the transformer comprises a primary winding and a secondary winding, the primary winding is connected with a switching device in series, and the primary winding and the switching device which are connected in series are connected with the first filter capacitor in parallel; the pulse width modulation module is used for sending out a driving pulse, and the driving pulse is used for driving the switching device to be switched on and off; and the negative temperature coefficient thermistor is connected between the alternating current power supply and the rectifying circuit in series. When the alternating current power supply is powered on, the negative temperature coefficient thermistor is used for limiting the current, so that the first filter capacitor cannot generate large impact current. And the negative temperature coefficient thermistor is connected between the alternating current power supply and the rectifying circuit in series, so that the soft start requirement can be met by only one negative temperature coefficient thermistor.

Description

Soft start auxiliary power supply circuit

Technical Field

The utility model belongs to the technical field of switching power supply, especially, relate to a soft start auxiliary power supply circuit.

Background

The input of the auxiliary power supply is generally alternating current input, alternating current is converted into pulsating direct current through a rectifying circuit, and then the pulsating direct current is filtered into smooth direct current through a capacitor. Because the filter capacitor exists, the capacity of the filter capacitor is often large, the initial voltage value on the capacitor is 0V, when the input voltage is switched on for the first time, a large impact current is generated, and the filter capacitor and a subsequent circuit are damaged, so that a soft start power circuit is urgently needed to be designed to inhibit the generation of the large impact current.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a soft start auxiliary power supply circuit can effectively restrain great impulse current's production, avoids causing the damage because of the electric current is too big to filter capacitor and back stage circuit.

To achieve the purpose, the utility model adopts the following technical proposal:

a soft-start auxiliary power supply circuit, comprising:

the rectification circuit is used for rectifying alternating current output by the alternating current power supply;

the first filter capacitor is used for filtering the rectified direct current;

the transformer comprises a primary winding and a secondary winding, the primary winding is connected with a switching device in series, and the primary winding and the switching device which are connected in series are connected with the first filter capacitor in parallel;

the pulse width modulation module is used for sending out a driving pulse, and the driving pulse is used for driving the switching device to be switched on and off;

and the negative temperature coefficient thermistor is connected between the alternating current power supply and the rectifying circuit in series.

As an optional technical solution of the present invention, the first filter capacitor is an electrolytic capacitor, the positive electrode of the first filter capacitor is connected to the rectifier circuit, and the negative electrode of the first filter capacitor is connected to the common terminal.

As an alternative technical scheme of the utility model, switching device includes first link, second link and control end, first link is connected primary winding, the second link is connected the common port, the control end is connected the output of pulse width modulation module.

As an optional technical solution of the present invention, the switching device is an MOS transistor.

As an optional technical scheme of the utility model, the output of pulse width modulation module with be connected with coupling resistor between the grid of MOS pipe.

As an optional technical solution of the present invention, the rectifier circuit is a bridge rectifier.

As an optional technical solution of the present invention, the secondary winding is further connected in series with a rectifier diode and a second filter capacitor.

As an optional technical solution of the present invention, the second filter capacitor is an electrolytic capacitor.

Compared with the prior art, the embodiment of the utility model provides a following beneficial effect has:

when an alternating current power supply is supplied, current is sent to a rectifying circuit through a negative temperature coefficient thermistor and rectified into direct current, then the direct current is filtered through a first filter capacitor and sent to a primary winding of a transformer, and then a driving pulse sent by a pulse width modulation module drives a switching device to be switched on and switched off, so that voltage is induced on a secondary winding of the transformer.

The embodiment of the utility model provides a pair of soft start auxiliary power supply circuit owing to be equipped with negative temperature coefficient thermistor, utilizes its negative temperature characteristic, and the temperature is higher its resistance lower more, consequently, when the alternating current power supply power transmission, carries out the current-limiting by negative temperature coefficient thermistor to make and to produce very big impulse current on the first filter capacitor, avoided causing the damage because of impulse current is too big to the circuit behind first filter capacitor and the first filter capacitor. And the negative temperature coefficient thermistor is connected between the alternating current power supply and the rectifying circuit in series, so that the soft start requirement can be met by only one negative temperature coefficient thermistor.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

The structure, ratio, size and the like shown in the present specification are only used for matching with the content disclosed in the specification, so as to be known and read by people familiar with the technology, and are not used for limiting the limit conditions which can be implemented by the present invention, so that the present invention has no technical essential significance, and any structure modification, ratio relationship change or size adjustment should still fall within the range which can be covered by the technical content disclosed by the present invention without affecting the efficacy and the achievable purpose of the present invention.

Fig. 1 is a circuit diagram of an auxiliary power supply for soft start according to an embodiment of the present invention.

Detailed Description

In order to make the objects, features and advantages of the present invention more obvious and understandable, the embodiments of the present invention are clearly and completely described with reference to the drawings in the embodiments of the present invention, and obviously, the embodiments described below are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

Referring to fig. 1, the present embodiment provides a soft-start auxiliary power circuit, which includes a negative temperature coefficient thermistor R2, a bridge rectifier REC, a first rectifying-filtering electrolytic capacitor C1, a high-frequency transformer T, MOS tube Q1, a pulse width modulation module PWM, a first rectifying diode D1, a second rectifying diode D2, a second rectifying-filtering electrolytic capacitor C2, and a third rectifying-filtering electrolytic capacitor C3.

The ac power supply has output terminals, one of which, IN _ L (typically the phase line), is connected to a first terminal of the bridge rectifier REC via a ntc thermistor R2, and the other of which, IN _ N (typically the neutral line), is connected to a second terminal of the bridge rectifier REC. The third end of the bridge rectifier REC is connected with the anode of the first rectifying and filtering electrolytic capacitor C1, and the fourth end of the bridge rectifier REC is connected with the common end GND. The cathode of the first rectifying and filtering electrolytic capacitor C1 is connected with the common terminal GND. The high-frequency transformer T includes a primary winding and two secondary windings. One end of the primary winding is connected with the positive electrode of the first rectifying and filtering electrolytic capacitor C1, the other end of the primary winding is connected with the drain D of the MOS tube Q1, the source S of the MOS tube Q1 is connected with the common end GND, and the gate G of the MOS tube Q1 is connected with the output end of the pulse width modulation module PWM through the coupling resistor R1.

One secondary winding is connected in series with a first rectifying diode D1 and a second rectifying and smoothing electrolytic capacitor C2. The other secondary winding is connected in series with a second rectifier diode D2 and a third rectifier-filter electrolytic capacitor C3.

Therefore, the working principle of the soft-start auxiliary power supply circuit provided by this embodiment is as follows:

when the alternating current power supply outputs the commercial power, the commercial power is sent to the bridge rectifier REC through the negative temperature coefficient thermistor R2, the bridge rectifier REC rectifies the commercial power into pulsating direct current, the pulsating direct current is filtered through the first rectifying and filtering electrolytic capacitor C1 to obtain smooth direct current, the smooth direct current is sent to the primary winding of the high-frequency transformer T, the MOS tube Q1 is driven to be switched on and switched off through driving pulses sent by the pulse width modulation module PWM, two groups of voltages are respectively induced on the two secondary windings, and the two groups of voltages are respectively rectified and filtered to generate two groups of power supplies V1 and V2.

Because the rectified and outputted electricity of the commercial power is pulsating direct current, a first rectifying and filtering electrolytic capacitor C1 with larger capacity must be added at the later stage for filtering so as to obtain the required smooth direct current. The initial voltage of the first rectifying and filtering electrolytic capacitor C1 is 0V, so once dc is suddenly applied, a large inrush current is inevitably generated, and the first rectifying and filtering electrolytic capacitor C1 and its subsequent circuits are easily damaged by the large inrush current. Therefore, IN this embodiment, a negative temperature coefficient thermistor R2 is connected IN series between the bridge rectifier REC and the ac power supply, that is, the thermistor is connected IN series to the output terminal IN _ L, and when the commercial power is first fed to the bridge rectifier REC, due to the current limiting function of the negative temperature coefficient thermistor R2, the first rectifying and filtering electrolytic capacitor C1 does not generate a large impact current, so that the impact of a large current on the first rectifying and filtering electrolytic capacitor C1 and the subsequent circuit is limited, thereby protecting the power supply. And, the thermistor is great with cement resistance compared, and is not fragile.

It should be noted that, IN this embodiment, the ntc thermistor R2 is connected IN series between the ac power supply and the bridge rectifier REC, that is, connected IN series to the output terminal IN _ L of the ac power supply, instead of being connected IN series to the bridge rectifier REC, so that the soft start requirement can be satisfied by using only one ntc thermistor R2. Of course, the same effect can be achieved by connecting the ntc thermistor R2 IN series to the output terminal IN _ N.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are intended to be inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed and illustrated, unless explicitly indicated as an order of performance. It should also be understood that additional or alternative steps may be employed.

The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.

Claims

1. A soft start auxiliary power supply circuit, comprising:

the first filter capacitor is used for filtering the rectified direct current;

2. The soft-start auxiliary power supply circuit according to claim 1, wherein the first filter capacitor is an electrolytic capacitor, an anode of the first filter capacitor is connected to the rectifying circuit, and a cathode of the first filter capacitor is connected to a common terminal.

3. The soft-start auxiliary power supply circuit according to claim 2, wherein the switching device comprises a first connection terminal, a second connection terminal and a control terminal, the first connection terminal is connected with the primary winding, the second connection terminal is connected with the common terminal, and the control terminal is connected with the output terminal of the pulse width modulation module.

4. A soft-start auxiliary power supply circuit as claimed in claim 3, wherein said switching device is a MOS transistor.

5. The soft-start auxiliary power supply circuit according to claim 4, wherein a coupling resistor is connected between the output end of the pulse width modulation module and the gate of the MOS transistor.

6. A soft-start auxiliary power supply circuit as claimed in claim 1, wherein said rectifying circuit is a bridge rectifier.

7. A soft-start auxiliary power supply circuit as claimed in claim 1, wherein said secondary winding is further connected in series with a rectifier diode and a second filter capacitor.

8. A soft-start auxiliary power supply circuit as claimed in claim 7, wherein said second filter capacitor is an electrolytic capacitor.